What Is Text-to-Speech, or TTS?

• "Speech synthesis (Text to speech) is the artificial production of human speech. A computer system used for this purpose is called a speech synthesizer, and can be implemented in software or hardware. A text-to-speech (TTS) system converts normal language text into speech; other systems render symbolic linguistic representations like phonetic transcriptions into speech."

TTS Software

• Asterisk flite: Can replace Festival in Asterisk
• asterisk-agi-audiotx: Asterisk AGI extension module that adds commands to allow the transfer of audio files to and from Asterisk via an AGI session
• asterisk-espeak: Asterisk dialplan application providing speech synthesis using the eSpeak text-to-speech engine
• Flite for asterisk 1.6 1.8 and 10
• espeak for asterisk 1.6 1.8 and 10
• Asterisk AGI script that uses Google's voice synthesis engine to render text to speech
• Speech synthesis using Microsoft Translator API for Asterisk
• Database Systems Corp.CTI technology with text to speech converter for IVR and voice broadcast applications.
• Festival
• asterisk-liambrola: Asterisk Dialplan application, which allows you to use Lia_Phon and Mbrola as a French speech synthesizer. Step by step instuctions on liambrola's installation under Asterisk (1.2, 1.4 and 1.6) can be found in this post: Speech synthesis in French under Asterisk.

Text-to-Speech tools

• Acapela Voices - including Arabic, Czech, Danish, Dutch (NL), Dutch (B), English (UK), English (US), Faroe, French, Finnish, German, Greek, Icelandic, Italian, Norwegian, Polish, Portuguese, Portuguese (Brazil), Russian, Spanish, Spanish (South America), Swedish and Turkish
• TextSpeak Text to Speech - Human sounding TTS in over 20 world languages packaged in hardware modules and standalone enclosures
• AT&T Labs voices - including German, French, Latin Am. ...